Nickel-containing flanges for use in direct resistance heating of platinum-containing vessels

A flange for use in direct resistance heating of a vessel which, during use, carries molten glass and which comprises an exterior wall which comprises at least 80 wt. % platinum, said flange comprising:

• (a) a plurality of electrically-conductive rings which, during use, form a conductive path for carrying current to the exterior wall, said plurality of rings comprising:
• (i) an innermost ring which is joined to and electrically connected with the vessel's exterior wall during use of the flange;
• and
• (ii) an outermost ring which receives electrical current during use of the flange;
• and
• (b) a cooling channel associated with the outermost ring through which a cooling fluid flows during use of the flange;
• wherein:
• (i) the innermost ring comprises a high-temperature metal which comprises at least 80 wt. % platinum;
• (ii) the outermost ring comprises at least 99.0 wt. % nickel;
• and
• (iii) the plurality of electrically conductive rings comprises a ring which (A) is located between the outermost and innermost rings and (B) comprises a platinum-nickel alloy which:
• (I) comprises more than 50 mole percent platinum,
• (II) comprises 10-20 wt. % nickel, and
• (III) during use of the flange, forms an adherent and protective scale which reduces the oxidation rate of the platinum-nickel alloy compared to pure nickel.